niVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 



1049 



Fig. 118. 



claimed that this plan will be found to save much time in cursory 

 examinations, such as medical men have frequently to make. 



In Fig, 118 A is the adapter, shown natural size (having the Society 

 screw, it fits any Microscope); this adapter contains a "sprung" 

 tube into which the tube B slides, carrying the optical part C (a 

 2-inch in the figure) at its lower end. All the objectives are composed 

 of the sliding-tube B and the optical part C, which together form one 

 piece about the usual size of an objective. In use, the adapter A is 

 kept screwed to the body of the instrument, and 

 the removal of B C from A is effected by simple 

 withdrawal, as in the case of an eye-piece, and 

 another power can thus be readily substituted. 



For the convenience of those who have ob- 

 jectives with the Society screw, the lower end of 

 the compound body of the Microscope is screwed 

 to the standard size, so that by simply unscrewing 

 the adapter which receives the objectives belong- 

 ing to the instrument, any standard glass may 

 be used. On the other hand, by sliding any 

 of the former objectives into the adapter when 

 thus unscrewed, they may be used on any other 

 standard instrument. The Society screw has not 

 been adopted for the optical part (joining C to B), 

 which, however, it would be advantageous to adopt 

 if it can be done mthout increasing the weight 

 to such an extent that the latter would slip down 

 out of the adapter. With the Society gauge, 

 any objectives might of course be ajiplied. At 

 present, the use of the sliding arrangement is 

 confined to the maker's own objectives. 



Instead of the " sprung " tube, the plan 

 adopted by Mr. Browning for astronomical eye- 

 pieces might, we think, be made use of with 

 advantage, viz. to make the sliding tube B not 

 cylindrical, but tapering, the " taper " being for a short distance 

 below the middle less rapid tliau at the middle part, the portion next 

 the collar being exactly cylindrical. 



Homogeneous - immersion Objectives for the Binocular, — 

 Fig. ll'J shows in natural size a ,'., hoiiio^ciicdus-immcrsiou objective 

 of Bowel] and Loahuid made as described by Mr. II. Gibbes at p. 373, 

 for use with the ordinary Weuham binocular, and showing both fields 

 fully illuminated. 



The lenses of the objective are contained within the lower part of B, 

 tlie u[»i)er portion of B being a very short adapter into which the 

 former can be screwed from behind. The back lens is thus brought 

 to within about a (juarter of an inch of the binocular prism. As the 

 objective is so mutli shortened it is necessary with most Microscopes 

 to have eitlier a super-stage or a special arrangenu'iit for allowing tlio 

 tube to be racked down that tiio objective may focus upon the object 

 on the ordinary stage. 



